Mixed filament yarn

ABSTRACT

Synthetic fibers having natural fiber-like touch, gloss, texture and appearance are produced by spinning a polyester and a polyamide through a common spinneret simultaneously to form mixed filaments consisting of multisegment filaments, in each of which the polyester is divided by the polyamide into at least three segments, and polyester single component filaments, drawing the mixed filaments and then subjecting the drawn mixed filaments to a false twisting to fibrillate the multisegment filaments.

States Patent [1 1 Matsui et a1.

[ Nov. 4, 1975 MIXED FILAMENT YARN [75] Inventors: Masao Matsui, Takatsuki; Susumu Tokura, Osaka; Masahiro Yamabe, Neyagawa, all of Japan [73] Assignee: Kanebo, Ltd., Tokyo, Japan 22 Filed: June 10', 1974 [21] Appl. No.: 478,064

Related U.S. Application Data [62] Division of Ser. No. 332,068, Feb. 13, 1973, Pat. No.

[30] Foreign Application Priority Data Feb. 24, 1972 Japan 4749451 [52] U.S. Cl. 57/140 BY; 57/140 J; 161/175; 264/171 [51] Int. Cl. D02G 3/04 [58] Field of Search..... 57/140 BY, 140 J; 264/103, 264/171, 174, 177 F; 161/175 [56] References Cited UNITED STATES PATENTS 3,627,868 12/1971 Funahashi 264/171 X 3,639,556 2/1972 Matsui et al. 264/171 3,660,993 5/1972 Matsui et al. 264/171 X 3,705,226 12/1972 Okamoto et a1. 264/174 X 3,718,534 2/1973 Okamoto et a1. 264/171 X 3,725,192 4/1973 Ando et al 264/177 F X Primary Examiner-John Petrakes Attorney, Agent, or FirmWoodhams, Blanchard and Flynn [57] ABSTRACT Synthetic fibers having natural fiber-like touch, gloss, texture and appearance are produced by spinning a polyester and a polyamide through a common spinneret simultaneously to form mixed filaments consisting of multisegment filaments, in each of which the polyester is divided by the polyamide into at least three segments, and polyester single component filaments, drawing the mixed filaments and then subject- 7 ing the drawn mixed filaments to a false twisting to fibrillate the multisegment filaments.

5 Claims, 8 Drawing Figures US. Patent Nov. 4, 1975 Sheet 1 of 2 3,916,611

F/GZ F/G5 Y iv 7/// V/ %\1@ W 1 H M X Sheet 2 of 2 3,916,611

US. Patent Nov. 4, 1975 MIXED FILAMENT YARN This is a division of application Ser. No. 332,068, filed Feb. 13, 1973, now US. Pat. No. 3,853,977.

The present invention relates to mixed filaments consisting of polyester and polyamide, which have different cross-sectional shapes.

Conventional polyester or polyamide fibers are excellent in dynamic properties but the fineness and crosssectional shape of each of the single component filaments are simple and therefore the touch, gloss, texture and appearance thereof are more simple than natural fibers.

In order to overcome this drawback, various attempts have been heretofore made but satisfactory results have not been obtained. For example, attempts have been made to spin filaments having different deniers from a common spinneret. The smallest denier of the monofilament obtained in this process is up to 1.5 denier, usually more than 2 deniers considering the operability, and from such filaments, it is difficult to obtain the desirable texture, touch and the like. As filaments provided with the natural fiber-like excellent properties, it is desirable to have a large number of filaments of non-circular cross-section of extremely fine denier, (for example, about 0.5 denier), and in order to keep a moderate resiliency and excellent dynamic properties, it is desired to have filaments having a denier several times as large as the extremely fine filaments.

Even if such filaments can be spun by the above described process, the filaments of an extremely fine denier and the filaments having a large denier are different in behavior in the spinning step (for example, solidification, speed, and the like), and it is difficult to find out the drawing condition suitable for any filaments in the subsequent drawing step, so that finally filaments poor in the dynamic property are formed.

The object of the present invention is to provide mixed filaments with both the preferable properties of synthetic fibers and natural fibers.

The present invention consists in mixed filaments (D) produced by a method, which comprises spinning a polyester and a polyamide through a common spinneret simultaneously to form an intermediate mixed filaments product (C) consisting of (A) multisegment filaments, in each of which the polyester is divided in cross section by the polyamide into at least three segments, and (B) polyester monofilaments, so as to satisfy the following definitions,

l. the ratio of the multisegment filaments (A) to the total mixed filaments (C) is 40 70% by weight,

2. the ratio of polyamide in each of the multisegments filaments (A) is less than 40% by weight, preferably less than 30% by weight and the ratio of polyamide in the total mixed filament product (C) is less than 30% by weight, preferably less than 25% by weight,

3. the polyamide in each multisegment filaments (A) forms thin layers having an even thickness which diverge radially in the cross-section of said multisegment filament (A), and

4. each polyester segment in the multisegment filament (A) is less than 1 denier, preferably less than 0.7 denier and the polyester monofilament (B) is more than 2 deniers, preferably more than? deniers, drawing the spun mixed filament product (C) and then subjecting the drawn mixed filament product (C) to a false twisting to fibrillate the multisegment filament (A) 2 contained therein and, thereby produce mixed filaments product (D).

The term segment used herein means that portion constituting the multisegment filament (A), which substantially extends evenly along the longitudinal direction of the filament. The term forming the thin layers having an even thickness diverging radially means a thin layer structure extending in at least three directions radially from one point, such as the Y-shape as shown in FIG. 1, the X-shape as shown in FIG. 2, and the six branches as shown in FIG. 3. Such radial thin layer structure can be easily formed as mentioned here.- inafter and such multisegment filaments can be efficiently separated by a false twisting and easily fibrillated.

The inventors have already found that such multisegment filament (filaments having the cross-sections as shown in FIGS. 1 to 3) is useful as proposed in Japanese Patent Application No. 29,925-1970. These fibers are very favorable on account of being similar to natural fibers in the texture, touch and gloss, but the fibers are poor in other respects. Namely, these fibers are too soft for use in gentlemens suit cloth or ladys thick suit cloth which requires a certain degree of resiliency, and are not suitable for them. If the fineness of the segment is enlarged (for example, 3 deniers) in order to overcome this drawback, the preferable properties as described above are lost.

The inventors have found that when the multisegment filaments and polyester single component filaments are simultaneously spun, the features of the above described multisegment filament are maintained and further a moderate resiliency can be obtained.

Namely, in order to attain the object of the present invention, the weight ratio of the multisegment filaments to the total mixed filaments simultaneously spun is 40 by weight. When the ratio of the multisegment filaments is less than 40% by weight, the excellent natural fiber-like properties cannot be obtained and when the rate is more than 70% by weight, the resulting fibers are too soft and deficient in the dimensional stability. That is, the ratio of the multisegment filaments must be selected within the above range depending upon the object.

Polyamide and polyester are different in their shrinkability, and in general polyamide is greater in shrinkage than polyester, that is, polyamide has less dimensional stability than polyester. Of course, if polyester is drawn at a low temperature, the shrinkability increases and may become the same as the shrinkability of polyamide, but yarn breakage occurs in the drawing step, and the drawing becomes unstable. When the mixed filaments composed of the multisegment filaments consisting of polyester and polyamide and the polyester single component filaments are drawn under a condition suitable for the polyester, the multisegment filaments are more highly shrunk and cause loose filaments (floating thread) and these filaments are not only entangled on the guide or traveller in the drawing but also cause hindrance in the after-treatments, such as false twisting, warp beaming, warping and the like. Consequently, in order to solve this problem, the ratio of polyamide to the multisegment filament must be decreased. As the result of various investigations, it has been found that the ratio of polyamide in the multisegment filaments must be less than 40% by weight, preferably less than 30% by weight and further the ratio of polyamide in the total mixed filaments must be less than 30% by weight,

3 preferably less than by weight.

In order to divide the polyester into at least 3 segments by the polyamide and to make small the ratio of polyamide in the multisegment filament as far as possible, it is most reasonable that the polyester and the polyamide are bonded in such a state that the polyamide forms thin layers having a substantially even thickness which diverge radially, in the cross-section of each of the above described multisegment filaments.

The of the cross-sections as shown in FIGS. 1 to 4 can be produced while maintaining a very stable bonding form as explained hereinafter. On the contrary, a filament as shown in FIG. 5, in which a component is divided with another component forming very uneven thin layers, is liable to cause aggregation of polymer in the spinning and a slight variation of the melt viscosity of both the components influences upon the bonded shape and it is difficult to produce such a filament having a uniform cross-sectional structure along the longitudinal direction and the fibrillation of the resulting filament is not effected efficiently.

In order to improve the fibrillation of the filament having such a cross-section, it is necessary to increase the rate of thin layer component, while in the filaments as shown in FIGS. 1 to 4 wherein a filament forming component is bonded by the radially diverged thin layers having an even thickness, it is easy to decrease the ratio of thin layer component to less than by weight and even if the ratio is reduced to about 10%, it is possible to maintain an even cross-sectional structure along the longitudinal direction 0 f the filament.

The larger the number of the polyester segments in each of the multisegment filaments, the higher is the advantage in view of the fibrillation, but when the number of segments is increased too much, the production is difficult and further it is difficult to divide the polyester evenly with a small amount of polyamide. In general, the number of polyester segments in each of the multisegment filaments is preferred to be 3 8, preferably 3 6.

The smallest polyester segment in the multisegment filament must be less than 1 denier. The extremely fine filaments obtained by fibrillation of such a filament have desirable texture, appearance and gloss similar to natural fibers. In general, the multisegment filaments composed of polyester segments having an even crosssection asshown in FIGS. 1 to 3 are useful, but in some cases, the multisegment filament as shown in FIG. 4, wherein the area and cross-sectional shape of the polyester segments are different, is preferable, because various forms of fibrils can be formed.

The polyester filaments spun simultaneously with the multisegment filaments serve to provide the moderate resiliency and excellent dynamic properties, which are characteristics of synthetic fibers, to the resulting fibers and a relatively large fineness, that is more than 2 deniers, usually about 3 1O deniers, is preferred.

The mixed filaments in which extremely fine fibrillated filaments and usual filaments (monofilament of 2 l0 deniers) are fully entangled, develop an excellent effect. These mixed filaments can be obtained by producing the multisegment filaments and single component filaments simultaneously and when the separately produced filaments are mixed, both the filaments are not fully entangled.

For a better understanding of the invention, reference is made to the accompanying drawings, wherein:

FIGS. 1 to 5 show embodiments of cross-sections of filaments;

FIG. 6 is a vertical cross-sectional view of spinneret which can produce the mixed filaments of the present invention;

FIG. 7 is a cross-sectional view of the spinneret as shown in FIG. 6 in the arrow direction on lines X-X; and

FIG. 8 is a cross-sectional view of the spinneret as shown in FIG. 6 in the arrow direction on lines Y-Y'.

The mixed fibers obtained by the method of the present invention can be produced in a high evenness of the cross-sectional structure by a relatively simple apparatus.

Referring to FIG. 6, an inner spinneret plate is superposed on a spinneret plate 110.

A part of the melted polyester is extruded from inner orifices 5 through a supplying chamber 2 and a passage 3 and the melted polyamide is extruded from channels 8 through a supplying chamber 1, passage 6 and a reservoir 7. Both the polymers are bonded at an inlet of a conduit 9 and spun from an orifice 111 through the conduit 9. On the other hand, a part of the remaining polyester is spun from an orifice 111 through a supplying chamber 2, a passage 4 and a conduit 9. Part number 120 is a supporter.

FIG. 7 is a cross-sectional view of the spinneret as shown in FIG. 6 in an arrow direction on lines X-X' and shows the bottom of the inner spinneret 100. The inner orifices 5 and the passages 4 are opened at the projecting portion of the bottom of the inner spinneret plate 100 corresponding to the spinning orifices 111 in the spinneret plate 110. The inner orifices 5 consist of four small holes. At the top face of the projecting portion in the bottom of the inner spinneret plate where each of the four small holesopens, channels 8 are provided between the outlets of the adjacent small holes.

FIG. 8 is a cross-sectional view of the spinneret as shown in FIG. 6 in an arrow direction on lines Y-Y' and shows the upper face of thespinneret plate provided with circular spinning orifices 111.

The spinneret as shown in FIGS. 6 to 8 provides the mixed filaments consisting of 3 multisegment filaments in which polyester is divided with four radially diverged polyamide thin layers into four segments and 3 polyester monofilaments.

By using a non-circular cross-sectional spinning orifice, non-circular cross-sectional filament can be easily obtained. However, considering the operability, the cross-section of the filament is preferred to be substantially circular. Furthermore, if the numbers of the inner orifices 5 and the channels 8 are varied, the multisegment filaments having the cross-section as shown in FIGS. 1, 3 and 4 can be easily obtained. The deniers of the multisegment filament and the polyester single component filament may be either the same or different, but when both the filaments have the same denier, the filaments having improved dynamic properties are apt to be obtained. The denier ratio of both the filaments is preferred to be about lO/7 7/10. A given value of the denier ratio of both the filaments can be obtained by selecting the diameter or length of the orifice 111. 1

When the filaments obtained by the above described method are applied to a false twisting, the segments in the multisegment filament are separated into fibrils and the polyester single component filaments and the fibrillated segments are fully entangled to form the desired mixed filaments. The fibrillation of the multisegment filament separates the polyester segments from the polyamide layers. The polyamide layers remain united to each other.

The term false twisting" used herein means that the filaments are twisted and then partially untwisted. The false twisting includes a usual false twisting (abbreviated to as FT process) wherein twisting and untwisting are effected continuously and a process wherein after twisting; twisting in the reverse direction is made (referred to as multi-step process). In general, Fl" process is preferred in view of the working efficiency and therefore an explanation will be made with respect to this process.

The object of the false twisting lies in fibrillation of the multisegment filament as mentioned above. The multisegment filament is readily fibrillated and therefore it is not necessary to determine the number of twistings (when a spindle is used, rotation number of spindle/yam velocity) exactly as in the usual twisting.

For the object of the present invention, the number of twist (false twisting) necessary per meter of filament is 0.1X 1.5 X, particularly 0.5X 1.2X (provided that, X 270,000/d+60+800, d denier of original fiber).

In the same manner, the twisting may be effected at room temperature (for example, 20C) or by heating (for example, 190C) and the feed ratio (velocity of feed roller/velocity of delivery roller) may be 0.8 2.0.

The above explanation was made with respect to PT process but FT process may be effected more than two times and further after the false twisting by FT process, a heat-setting and conventional twisting may be effected.

Then, an explanation will be made with respect to the multi-step process.

This process may combine two steps of twisting reverse twisting, three steps of twising heat setting reverse twisting, four steps of twisting heat setting reverse twisting heat setting or may combine further many steps.

In this case, the number of twists for effecting fibrillation (usually the first step) is the same as in the above described FT process. The number of twists in the reverse direction effected thereafter may be the same as or different from the original number of twists but is preferred to be at least 50, preferably at least 70% of the original number of twists. When the original number of twists is different from the number of reverse twists, the fibers are actually twisted and the number of actual twists and the direction thereof can be selected depending upon the object.

The false twisting effected in FT process may be carried out by a conventional false twisting machine provided with a false twisting portion consisting of a spindle between a feed roller and a delivery roller and a heating portion consisting of an electric heater or may be carried out by providing a false twisting portion between a delivery roller of a drawing apparatus and a winding up apparatus to effect the drawing and false twisting continuously.

As the false twisting portion, use may be made of conventional means, for example, a spindle, a means for applying false twists to filaments directly by contacting the filaments with a rotating roller, that is a means for applying twists directly by a friction and air jet type means which applies false twists to filaments by a rotating flow of compressed air.

As the heating portion, use may be made of conventional plate-shaped or tube-shaped heating elements but as mentioned above. Any heating element may not be used depending upon the purpose. In the multi-step process, conventional twisters (double twister, uptwister and the like) may be used. The heat-setting may be effected by the following means. That is, a bobbin wound with filaments is heated with steam or hot water or the running filament is heated by a metal heater or a heater tube. By the method of the present invention, various fibers can be obtained.

As polyesters to be used in the present invention, mention may be made of polyethylene therephthalate, polyethylene oxybenzoate, polytetramethylene terephthalate, polydimethylcyclohexane terephthalate, polypivalolactone and copolyesters containing the components of these polyesters.

As polyamides to be used in the present invention, mention may be made of nylon 6, nylon 66, nylon l l, polymethaxylene adipamide and copolymers containing the components of these polyamides.

The combination of polyester and polyamide to be used in the present invention can be selected optionally depending upon the object but when highly crimped filaments are to be obtained by applying false twists, it is preferred to combine polyester and polyamide, which are equal in the appropriate false twisting conditions, for example, a combination of polyethylene terephthalate and nylon 66.

The following examples are given for the purpose of illustration of this invention and are not intended as limitations thereof.

EXAMPLE I By using the spinneret as shown in FIG. 6, provided that 18 orifices 111 are arranged in a circumference of a spinneret plate 110 and 9 groups'of inner orifices 5 and channels 8, and 9 passages 4 are opened on the bottom of the inner spinneret alternately corresponding to the orifices 111, polyethylene terephthalate (PET) having an intrinsic viscosity of 0.71 in ochlorophenol solution at 30C and polyhexamethylene adipamide (nylon 66) having an intrinsic viscosity of 1.05 in metacresol at 30C are melted separately and the melted PET and the melted nylon 66 are supplied to a supplying chamber 2 and a supplying chamber 1 in a weight ratio 7/1 by metering pump respectively. The temperature of the spinneret is maintained at 290C and both the melted polymers are spun from circular orifices, each having a diameter of 0.25 mm, and cooled in air and the spun filaments are wound up at a velocity of 700 m/min, while oiling, drawn to 3.6 times on a drawing pin at C, and wound up while contacting with a metal plate at 165C for about 0.1 sec. to obtain drawn yarns of 75 denier/ 18 filament, which is referred to as yarn F The yarn F is composed of 9 polyester single component filaments and 9 multisegment filaments having the cross-section as shown in FIG. 2 wherein PET is divided by thin layers of nylon 66 into 4 segments and four segments are uniformly dispersed (conjugate ratio of PET/nylon 66 being 3/1 For comparison, the multisegment filament and the polyester single component filament are separately spun and drawn.

Namely, by using a spinneret as shown in FIG. 6, provided that 18 orifices 111 are arranged on a spinneret plate and 18 groups of inner orifices 5 and channels 8 corresponding to said orifices 111 are provided 7 on the inner spinneret plate 100, PET and nylon 66 are spun and drawn in the same manner as in the production of yarn F provided that the feed ratio of PET/nylon 66 is 3/1 by weight, whereby multisegment filaments of 75 denier/18 filament are obtained, which is referred to as yarn F Separately, PET is spun in a conventional process to form PET filaments having 75 denier/ l 8 filament, which is referred to as yarn F Yarns F F and F are false twisted and then fed into a metal tube heater having an inner diameter of 3 mm and a length of 50 cm heated at 215C and taken out at a rate of 60 m/min through a spindle rotating at 200,000 rpm and wound up at a rate of 55 m/min.

After the false twisting, the yarns P and F are completely fibrillated and in the yarn F 1 the fibrillated segments and the polyester single component filaments are thoroughly entangled and dispersed homogeneously, each of the above false twisted yarns is S-twisted and Z-twisted and these twisted yarns are mixed and then formed into a plain knitted goods by a circular knitting machine of 20 gauge and these knitted goods are refined, dyed and steam set to form suit cloths.

The resulting suit cloths are estimated and the results are shown in the following Table 1.

Table 1 Shape retaining Yarn Bulkiness Resiliency Softncss property F present o o o invention F Comparative x o x F Comparative o x 0 ln Table l. omcans good. means fair and X mcans poor.

In Table l, 0 means good, A means fair and X means poor.

In the above Table, the bulkiness, resiliency and softness are feeling estimation and the shape retaining property is estimated by classifying the deformation, after a square form of the suit cloth is washed times into three classes.

As seen from Table 1, the suit cloth obtained by using the mixed yarn F produced by the method of the present invention is rich in bulkiness and has a moderate resiliency and further softness and an excellent shape retaining property and is provided with the features of natural fibers and synthetic fibers.

EXAMPLE 2 The mixed filaments are produced in substantially the same manner as in the yarn F in Example 1, provided that the feed ratio of PET/nylon 66 is varied to 3/ 1 5/1, 7/ 1 and 9/ 1. When the feed ratio of PET/nylon 66 is 3/1, the conjugate ratio of PET/nylon 66 in the multisegment filament is substantially l/l. When the feed ratios are 5/1, 7/ l and 9/1, the conjugate ratios are substantially 2/1, 3/1 and 4/1, respectively. When the conjugate ratio of PET/nylon 66 of multisegment filament is Ill and 2/1, that is when the rate of polyamide in the multisegment filament is 50 and 33%, the yarns wound on bobbins after drawing float loose filaments and cause hindrance in the following false twisting step.

On the other hand, when the conjugate ratio is 3/1, that is when the rate of polyamide in the multisegment filament is 25%, the amount of the loose filaments is small and there is no hindrance in the following step. In the yarn of a conjugate ratio of 4/1 wherein the rate of polyamide in the multisegment filament is 20%, there is no loose filament.

EXAMPLE 3 e-polycaproamide (nylon 6, intrinsic viscosity in the metacresol solution at 30C being 1.1) and PET are spun and drawn in the same manner as described in Example 1 in a feed ratio of PET/nylon 6 being 9/ 1 to obtain yarn F cf 75 denier/ 18 filament. The resulting yarn F is false twisted. The thus treated yarns are fed at a rate of 60 m/min without using a heater and taken out at a rate of 60 m/min through a false twisting spindle rotating at 1,900,000 rpm and wound up at a rate of 61.2 m/min.

The multisegment filaments in the yarn F after the false twisting are fibrillated. The yarn F after the false twisting is not substantially crimped and is flexible and has a moderate resiliency and shows silk-like gloss.

What is claimed is:

1. An article of manufacture, a yarn consisting essentially of a mixture of (A) a component consisting of fibrillated composite filaments of polyester and polyamide in each of which the polyester is divided in cross section into at least three segments by thin cross sectional layers of polyamide having a uniform thickness and which in cross section diverge radially and (B) a component consisting of polyester monofilaments; said components (A) and (B) being mixed homogeneously and entangled with each other, the ratio of component (A) to total yarn being 40 to by weight, the ratio of polyamide to the total yarn being less than 30% by weight, the ratio of polyamide to component (A) being less than 40% by weight, each polyester segment of component (A) being less than 1 denier and said polyester filaments of component (B) being more than 2 deniers,

said component (A) being fibrillated by drawing and false twisting a yarn consisting of composite filaments of (A) and filaments of component (B).

2. The article of claim 1 in which the polyamide is polyhexamethylene adipamide.

3. The article of claim 1 in which the polyamide is epolycaproamide.

4. The article of claim 1 in which the polyester is polyethylene terephthalate.

5. The article of claim 1, in which said polyamide is selected from the group consisting of polyhexamethylene adipamide, e-polycaproamide and copolyamides thereof, and said polyester is selected from the group consisting of polyethylene terephthalate and copolyesters thereof. 

1. AN ARTICLE OF MANUFACTURE, A YARN CONSISTING ESSENTIALLY OF A MIXTURE OF (A) A COMPONENT CONSISTING OF FIBRILLATED COMPOSITE FILAMENTS OF POLYESTER AND POLYAMIDE IN EACH OF WHICH THE POLYESTER IS DIVIDED IN CROSS SECTION INTO AT LEAST THREE SEGMENTS BY THIN CROSS SECTIONAL LAYERS OF POLYAMIDE HAVING A UNIFORM THICKNESS AND WHICH IN CROSS SECTION DIVERGE RADIALLY AND (B) A COMPONENT CONSISTING OF POLYESTER MONOFILAMENTS, SAID COMPONENTS (A) AND (B) BEING MIXED HOMOGENEOUSLY AND ENTANGLED WITH EACH OTHER, THE RATIO OF COMPONENT (A) TO TOTAL YARN BEING 40 TO 70% BY WEIGHT, THE RATIO OF POLYAMIDE TO THE TOTAL YARN BEING LESS THAN 30% BY WEIGHT, THE RATIO OF POLYAMIDE TO COMPONENT (A) BEING LESS THAN 40% BY WEIGHT, EACH POLYESTER SEGMENT OF COMPONENT (A) BEING LESS THAN 1 DENIER AND SAID POLYESTER FILAMENTS OF COMPONENT (B) BEING MORE THAN 2 DENIERS,
 2. The article of claim 1 in which the polyamide is polyhexamethylene adipamide.
 3. The article of claim 1 in which the polyamide is epsilon -polycaproamide.
 4. The article of claim 1 in which the polyester is polyethylene terephthalate.
 5. The article of claim 1, in which said polyamide is selected from the group consisting of polyhexamethylene adipamide, epsilon -polycaproamide and copolyamides thereof, and said polyester is selected from the group consisting of polyethylene terephthalate and copolyesters thereof. 